Drilling performance becomes inefficient by the presence of vibrational effect which is stick and slip. This situation is a source of failure which reduce penetration rate, increase operating time, and contribute to increase drilling operating costs.This is due to the surface alternating between sticking to and sliding over each other, with a corresponding change in the force of friction. Only if kinetic friction is bigger enough to encounter this static friction, it can cause a sudden jump in the velocity of the movement, condition characterized by fluctuations in the rotational speed of BHA. The main objective is to come out with a solution in reducing stick and slip.First, the problem is encountered by means of the alignment of different drilling parameters, such as rotary speed, drilling torque and weight on bit. This conventional control technique required expertise from driller. Second, by introducing a roller reamer, the more effective control methodology. Roller cutters from the roller reamer rotate around the wall and it is able to provide low torque point of stabilization. It transforms the interaction between borehole and contact points by introducing a low-friction bearing between BHA and borehole wall.As a result, implementation of roller reamer shows the constant transmission of rotational energy, thus able to improve the weight to the bit. Two offset wells have been selected for this case study, with well #1 exercising conventional method while well #2 makes use of roller reamer. Stick slip effect reduces from 180% srpm to 30% srpm. Furthermore, it is able to save 40% of drilling time on that particular section. This paper focuses on the practical solution by implementing roller reamer to mitigate stick slip effect base on actual field scenario. A comparisons and conceptual models are provided as well as the illustration of its configuration.
The SB Field is located in Block PM on the west side of the Malay Basin, Malaysia. It is notorious for its steeply rising pressure ramp, narrow drilling operation window and inter-bedded sand, coal, and shale formations. Block PM is still at the exploration and appraisal stage with limited petrophysical information. Well SBD-2 was the second attempt to reach and cross the F & H sands of this basin. Despite using managed pressure drilling, the first attempt failed when an influx exceeded the fracture gradient, resulting in total fluid losses. Due to the shallow pressure ramp and narrow window between pore pressure and fracture gradient, a repeat attempt was initially deemed "un-drillable". However, the design team felt the target could be reached using an automated managed pressure drilling technology. The team was able to maintain constant bottom hole pressure over three demanding hole sections and reach target total depth. The 8-1/2" × 14-3/4" section required minimum overbalance to manage "wellbore breathing" and to control potential losses to weaker horizons. In the 10-1/2" × 12-1/4" section, the system was used to identify and react quickly to kicks in high pressure sands and also to eliminate wellbore breathing/ballooning. In the final 8-1/2" × 9-1/2" section, the objective was to maintain overbalance in the narrow pressure window between pore pressure and fracture gradient. This paper will describe the design efforts employed while preparing to drill the SBD-2 well. The challenges and lessons learned, particularly managing pore pressure prediction with multiple techniques will be discussed. Lessons learned and recommended workflows for similar projects will also be outlined.
In 2012, a redevelopment infill drilling campaign took place in a brown field, offshore Malaysia. Accurate wellbore positioning was critical to place a well within a path that navigates 2200 ft through an antithetic faults panel, separated approximately 900 ft, and with a 120 ft general throw; and to intersect the five target reservoirs of the well. The complex well path also faced the challenges of infill drilling in a brown field, such as collision avoidance in a crowded field, the location of the target reservoirs relative to the available drilling slots; as well as trajectory restrictions due to completions design. This paper presents the well design solutions that include a rigorous anti-collision analysis and a comprehensive survey programme. The survey programme consists of gyro while drilling (GWD) on the upper section of the well until the path is clear of magnetic interference from neighboring wells and the application of in-field referencing (IFR) correction for conventional measurement while drilling (MWD) magnetic survey based on accelerometers and magnetometers. IFR improves survey accuracy with a multi-station analysis that corrects the survey error with the localised crustal effects in the magnetic field of the earth. It was used for well positioning in between faults and for target intersection. It enabled drilling the well with higher confidence while intersecting the target reservoirs. A reduction of 60% on survey uncertainty was observed. The more accurate wellbore survey also optimises collision analysis for future well plans and it gives more reliable control points to update the subsurface static model. The benefits were obtained without compromising the drilling performance given that no extra operational time is required for the survey correction. Introduction Context The well is located in a brown field, offshore Malaysia. Three infill drilling campaigns have been executed since a decade ago to increase oil recovery. To maximise the use of existing assets and to optimise cost, infill drilling has been performed from existing drilling facilities by either accommodating new drilling slots or side-tracking idle wells. The well was planned to target several reservoirs located in crestal position in the southern block of a rollover anticline formed by growth faulting. In the study area, faults show a general east-west trending direction. The reservoirs are entirely related to sealing against faults while within reservoirs the seals are marine flooding surfaces. Well design considerations The well design process consisted of identifying the available surface location -a well with high water cut, idle since 2007- and selecting the subsurface targets. Once drilling targets were identified and preliminary well trajectories were built, an integrated team approach was used to optimise the well paths, usually requiring a compromise between the desired and the practical approach.
Enhanced Magnetic surveying technique was introduced to Field Q in Malaysia allowing the tight geological target requirements to be achieved without impacting the operator’s drive for drilling efficiency. Managing wellbore uncertainty is a significant challenge in Field Q, West Malaysia, where the Subsurface Team defines tight reservoir targets to accommodate the uncertainties that they have in a long step out well. Accurate well positioning becomes crucial in this situation to allow the penetration of multiple small targets. Historical approaches would have involved either running gyro surveys (which introduce more risk and time to the drilling process), or having to "over engineer" the wells (by creating tortuous well paths and drilling on the line to achieve the small drilling targets) due to the uncertainties of standard MWD surveys. Both of these approaches are against the drive to continually improve drilling efficiency while reducing risks. Magnetic surveying has become increasingly accurate and now provides a cost-effective alternative to gyroscopic surveys in real-time drilling applications. New techniques for identifying and compensating for these errors involve a better understanding of the natural variations in the earth’s magnetic field, and new methods of mapping local variations improve magnetic modeling. The enhancement involves a multi-station analysis technique that provides compensation for drillstring magnetic interference and further improved when used in conjunction with geomagnetic referencing, which takes account of localized crustal effects in the earth’s magnetic field. With a Geomagnetic Referencing System in Field Q, magnetic survey reduced uncertainty by 60% on average compared to a standard MWD error model. The benefits from this real-time drilling surveying process also means drilling is more accurate, with a reduced need for correction runs, or post-drilling changes to the planned well trajectory.
Two significant development projects were being planned for brownfields in southeast Asia with a total of seven platforms and 230 wellbores in place. Previous drilling campaigns were conducted from 10 to 30 years ago. Hence, existing data were of variable quality and reliability. During the design process for both fields, it was determined that there were large discrepancies and irregularities between well positioning databases. This not only complicated the anticollision situation of drilling in the congested fields but could also influence the reservoir model accuracy for determining the development target. The anticollision risks based on the existing data meant that well plans had to be "over engineered" to avoid the perceived risks while also requiring offset wells to be shut in during drilling operations. Thus, both drilling efficiency and production were affected because of the well positioning uncertainties. A comprehensive survey management process was embarked upon by both the operator and service company to ensure that the survey databases being used by the drilling and subsurface teams were consistent and free from gross errors. This included the review of all existing survey reports, sources of platform positions, etc. to identify anomalies or gross errors. This was the first such project conducted by the operator. This paper discusses the complete survey management validation process and also highlights its effect in allowing the safe and efficient well planning of the drilling campaigns while providing the subsurface team an accurate well positioning database to allow accurate target selection.
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